112 THE CANADIAN ENTOMOLOGIST. 



attention to collecting and determining the insects." He was helped in 

 this work by specialists in Diptera and Coleoptera, and had himself to 

 work out and describe many species of Hymenoptera : to out of 14 

 species of Oxybehis, 28 out of 30 of Ajidj-ena, and at least 30 other 

 species of Andrenidsie. The descriptions of these have appeared in the 

 Trans. Am. Ent. Soc, 1889-1893. 



The two great agencies of cross-fertilization of flowers are the wind 

 and insects ; hence Mr. Robertson has thus been led to notice some in- 

 teresting facts concerning the effect of wind on bees and flowers. (Bot. 

 Gaz.,XIII., 1888, p. 11). 



The first papers by Mr. Robertson are on the pollination of Asclepias, 

 the flowers of which are most interesting in their peculiar adaptation for 

 cross-fertilization by the agency of insects. Their structure and the great 

 difficulty the smaller insects have in effecting pollination, lead Mr. 

 Robertson to believe that "bumble-bees have had most influence in 

 modifying the flowers, and they are the most common visitors after the 

 hive bees. Hive bees, it is to be remembered, do not belong to our fauna.'' 



Our space is too limited to allow us to follow the writer into what he 

 has observed in all the different orders and species of flowering plants 

 studied ; but the names of all the insects observed visiting the flowers 

 are given, as well as tabular data of the respective number of visitors of 

 the different classes — Hymenoptera, Diptera, Lepidoptera, Coleoptera 

 and Hemiptera. 



As an instance, it may be mentioned that on the flowers of Ceanothus 

 Americanus there were seen 48 species of Hymenoptera, 45 of Diptera, 2 

 of Lepidoptera, 13 of Coleoptera, and 4 of Hemiptera; and considera- 

 tions are given, as in the case of all other blossoms treated of, on the 

 arrangement of the flowers, their form, colour and other peculiarities of 

 structure, some of them exceedingly minute, in which close and patient 

 observation often succeeds in discovering most wonderful purpose and 

 design for insuring cross-fertilization. These investigations are of great 

 interest, and we commend them to the attention of Entomologists and 

 Botanists as a fertile field of useful special study. Our idea in mention- 

 ing these excellent articles of Mr. Robertson's is to draw to this subject 

 the attention it deserves from Entomologists, who from their place of 

 publication might not be aware of their existence. 



J. A. GUIGNARD ASJD J. Fl-ETCHER. 



